In a medium saucepan, bring the lentils and water to a boil, lower the heat, cover, and cook for 30 minutes until tender. Drain.
In a medium skillet, steam the onion, mushrooms, and celery in the water, stirring to prevent sticking.
Mix all of the ingredients together.
Shape into patties and cook on a lightly oiled skillet, or bake in a 350 oven for 20 minutes. Turn once to brown on both sides.